U.S. patent application number 13/203423 was filed with the patent office on 2011-12-29 for radio communication system, radio base station, and blockade control method.
This patent application is currently assigned to KYOCERA CORPORATION. Invention is credited to Shinji Nakano.
Application Number | 20110319125 13/203423 |
Document ID | / |
Family ID | 42665607 |
Filed Date | 2011-12-29 |
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United States Patent
Application |
20110319125 |
Kind Code |
A1 |
Nakano; Shinji |
December 29, 2011 |
RADIO COMMUNICATION SYSTEM, RADIO BASE STATION, AND BLOCKADE
CONTROL METHOD
Abstract
A radio base station (1), which is to be pre-blockaded,
transmits a pre-blockade initiate notification to radio base
stations (2A-2F) neighboring the radio base station (1). Further,
the radio base station (1) reduces the transmission power thereof
at a predetermined reduction rate at a initiation time of the
pre-blockade. Meanwhile, each of the radio base stations (2A-2F)
receives the pre-blockade initiate notification and increases the
transmission power at a predetermined increase rate at the
initiation time of the pre-blockade, the absolute value of
predetermined increase rate being equal to that of the
predetermined reduction rate at the radio base station (1).
Inventors: |
Nakano; Shinji; (Kanagawa,
JP) |
Assignee: |
KYOCERA CORPORATION
Kyoto
JP
|
Family ID: |
42665607 |
Appl. No.: |
13/203423 |
Filed: |
February 25, 2010 |
PCT Filed: |
February 25, 2010 |
PCT NO: |
PCT/JP2010/053002 |
371 Date: |
August 25, 2011 |
Current U.S.
Class: |
455/522 |
Current CPC
Class: |
H04W 52/28 20130101;
H04W 52/04 20130101; H04W 52/44 20130101; H04W 52/287 20130101;
H04W 52/60 20130101 |
Class at
Publication: |
455/522 |
International
Class: |
H04W 52/04 20090101
H04W052/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2009 |
JP |
2009-043192 |
Jun 17, 2009 |
JP |
2009-144055 |
Claims
1. A radio communication system comprising: a first radio base
station; and a second radio base station neighboring the first
radio base station, wherein the first radio base station includes:
a storage unit configured to store information on the second radio
base station; a pre-blockade initiate notification transmitter
configured to transmit a pre-blockade initiate notification
indicating initiation of a pre-blockade to the second radio base
station identified based on the information on the second radio
base station stored in the storage unit, in initiating the
pre-blockade; and a transmission-power reduction processor
configured to reduce transmission power, and the second radio base
station includes: a pre-blockade initiate notification receiver
configured to receive the pre-blockade initiate notification; and a
transmission-power increase processor configured to increase
transmission power upon receiving the pre-blockade initiate
notification from the pre-blockade initiate notification
receiver.
2. The radio communication system according to claim 1, wherein the
transmission-power reduction processor reduces the transmission
power in decrements of a predetermined amount in a predetermined
time period, and the transmission-power increase processor
increases the transmission power in increments of the predetermined
amount in the predetermined time period.
3. The radio communication system according to claim 1, wherein the
first radio base station includes a distance measuring unit
configured to measure a distance between the first radio base
station itself and the second radio base station, and the
pre-blockade initiate notification transmitter transmits the
pre-blockade initiate notification to the second radio base
station, the distance from which to the first radio base station
measured by the distance measuring unit is equal to or smaller than
a predetermined threshold.
4. The radio communication system according to claim 1, wherein the
second radio base station includes a direction specifying unit
configured to specify a direction in which the first radio base
station exists, and the transmission-power increase processor
increases the transmission power in the direction in which the
first radio base station exists, the direction being specified by
the direction specifying unit.
5. The radio communication system according to claim 1, wherein the
first radio base station includes an ongoing-call absence
notification transmitter configured to transmit the second radio
base station an ongoing-call absence notification indicating that
there is no on-going call anymore, when there is no ongoing call
anymore in the first radio base station, the second radio base
station includes an ongoing-call absence notification receiver
configured to receive the ongoing-call absence notification, and
the transmission-power increase processor stops increasing the
transmission power when the ongoing-call absence notification
receiver receives the ongoing-call absence notification.
6. The radio communication system according to claim 1 further
comprising a base station controller configured to connect the
first radio base station and the second radio base station to each
other and to control the first radio base station and the second
radio base station, wherein the pre-blockade initiate notification
transmitter transmits the pre-blockade initiate notification to the
second radio base station via the base station controller.
7. A radio base station constituting a radio communication system,
the radio base station comprising: a storage unit configured to
store information on a different radio base station neighboring the
radio base station itself; a pre-blockade initiate notification
transmitter configured to transmit a pre-blockade initiate
notification indicating initiation of a pre-blockade to the
different radio base station identified based on the information on
the different radio base station stored in the storage unit, in
initiating the pre-blockade; and a transmission-power reduction
processor configured to reduce transmission power.
8. A radio base station constituting a radio communication system,
the radio base station comprising: a pre-blockade initiate
notification receiver configured to receive a pre-blockade initiate
notification from a different radio base station, the pre-blockade
initiate notification indicating initiation of a pre-blockade in
the different radio base station; and a transmission-power increase
processor configured to increase transmission power when the
pre-blockade initiate notification receiver receives the
pre-blockade initiate notification.
9. A blockade control method in a radio communication system
including a first radio base station and a second radio base
station neighboring the first radio base station, the method
comprising the steps of: the first radio base station transmitting
a pre-blockade initiate notification indicating initiation of a
pre-blockade to the second radio base station identified based on
information on the second radio base station stored in a storage
unit, when the first radio base station initiates the pre-blockade;
the first radio base station reducing transmission power; the
second radio base station receiving the pre-blockade initiate
notification; and the second radio base station increasing
transmission power upon receiving the pre-blockade initiate
notification.
10. A radio communication system comprising a first radio base
station; and a second radio base station neighboring the first
radio base station, wherein the first radio base station includes:
a storage unit configured to store information on the second radio
base station; a transmitter configured to transmit a preparation
signal to the second radio base station identified based on the
information on the second radio base station stored in the storage
unit, before blockade processing is performed; and a
transmission-power reduction processor configured to reduce
transmission power, and the second radio base station includes a
receiver configured to receive the preparation signal; a
transmission-power increase processor configured to increase
transmission power in accordance with the preparation signal
received by the receiver.
11. The radio communication system according to claim 10, wherein
the transmission-power reduction processor reduces the transmission
power in accordance with a transmission-power reduction rate, and
the transmission-power increase processor increases the
transmission power in accordance with a transmission-power increase
rate.
12. The radio communication system according to claim 10, wherein
the first radio base station includes a distance measuring unit
configured to measure a distance between the first radio base
station itself and the second radio base station, and the
transmitter transmits the preparation signal to the second radio
base station, the distance from which to the first radio base
station measured by the distance measuring unit is equal to or
smaller than a predetermined threshold.
13. The radio communication system according to claim 10, wherein
the second radio base station includes a direction specifying unit
configured to specify a direction in which the first radio base
station exists, and the transmission-power increase processor
increases the transmission power in the direction in which the
first radio base station exists, the direction being specified by
the direction specifying unit.
14. The radio communication system according to claim 10, wherein
the first radio base station includes an ongoing-call absence
notification transmitter configured to transmit the second radio
base station an ongoing-call absence notification indicating that
there is no on-going call anymore, when there is no ongoing call
anymore in the first radio base station, the second radio base
station includes an ongoing-call absence notification receiver
configured to receive the ongoing-call absence notification, and
the transmission-power increase processor stops increasing the
transmission power when the ongoing-call absence notification
receiver receives the ongoing-call absence notification.
15. The radio communication system according to claim 10 further
comprising a base station controller configured to connect the
first radio base station and the second radio base station to each
other and to control the first radio base station and the second
radio base station, wherein the transmitter transmits the
preparation signal to the second radio base station via the base
station controller.
16. A radio base station which performs blockade processing
comprising: a storage unit configured to store information on a
different radio base station neighboring the radio base station
itself; a transmitter configured to transmit a preparation signal
to the second radio base station identified based on the
information on the different radio base station stored in the
storage unit, before blockade processing is performed; and a
transmission-power reduction processor configured to reduce
transmission power.
17. A radio base station connected to a blockade radio base station
which performs blockade processing, the radio base station
comprising: a receiver configured to receive a preparation signal
transmitted from the blockade radio base station before the
blockade processing is performed; and a transmission-power increase
processor configured to increase transmission power in accordance
with the preparation signal received by the receiver.
18. The radio communication system according to claim 10, wherein
the first radio base station includes: a blockade processor
configured to measure a reception level of the second radio base
station when there is no ongoing call anymore in the first radio
base station itself; and a transmission-power-change stop
notification transmitter configured to transmit a
transmission-power-change stop notification to the second radio
base station, the reception level of which measured by the blockade
processor has reached or exceeded a threshold, and the second radio
base station includes a transmission-power-change stop notification
reception processor configured to stop the increase of the
transmission power upon receiving the transmission-power-change
stop notification.
Description
TECHNICAL FIELD
[0001] The present invention relates to a radio communication
system including multiple radio base stations, a radio base station
in the radio communication system, and a blockade control method in
the radio communication system.
BACKGROUND ART
[0002] In a radio communication system, a radio base station
performs processing (blockade processing) to turns off transmission
power in the case where maintenance or the like of the radio base
station is to be performed. In the blockade processing, the radio
base station is set to receive no new call which is a call newly
made by a radio terminal. Moreover, if there is an ongoing call
which is a call currently in communication between the radio
terminal and the radio base station, the radio base station waits
until the ongoing call is terminated, and turns off transmission
power after the termination. Such processing of waiting the
termination of ongoing call is called pre-blockade processing. Note
that, if there is an ongoing call even after a predetermined time
period from the start of the blockade processing, the radio base
station forcefully disconnects the ongoing call, and turns off the
transmission power (For example, see Patent Document 1).
PRIOR ART DOCUMENT
Patent Document
[0003] Patent Document 1: Japanese Patent Application Publication
No. 2006-5395
SUMMARY OF THE INVENTION
[0004] However, in the method of the conventional blockade
processing described above, if a radio terminal located in a
coverage area (cell) of a radio base station before the blockage
processing becomes located outside the cell due to the blockage
processing, the radio terminal cannot receive anymore a new call
which can be received before the blockage processing. In other
words, an area where a communication service cannot be received
occurs due to the blockade.
[0005] In another case, if the radio terminal is located outside
the cell due to the blockade processing, the radio terminal makes a
request to accept a new call to a different radio base station
neighboring the blockaded radio base station, i.e. a different
radio base station located away from the radio terminal. In this
case, even if the new call is accepted, the communication quality
may be deteriorated.
[0006] Moreover, in the method of the conventional blockade
processing described above, the ongoing call is forcefully
disconnected after the predetermined time period from the start of
the blockade processing. This causes deterioration in the quality
of communication service.
[0007] In view of the above problem, an object of the present
invention is to provide a radio communication system, a radio base
station, and a blockade control method for preventing deterioration
of quality of communication service.
[0008] To solve the above problem, the present invention has
following features. A first feature of the invention is summarized
as a radio communication system (radio communication system 100)
including: a first radio base station (radio base station 1); and a
second radio base station (radio base stations 2A to 2F)
neighboring the first radio base station, wherein the first radio
base station includes: a storage unit (storage unit 103) configured
to store information on the second radio base station; a
pre-blockade initiate notification transmitter (pre-blockade
initiate notification transmitter 154) configured to transmit a
pre-blockade initiate notification indicating initiation of a
pre-blockade to the second radio base station identified based on
the information on the second radio base station stored in the
storage unit, in initiating the pre-blockade; and a
transmission-power reduction processor (transmission-power
reduction processor 156) configured to reduce transmission power,
and the second radio base station includes; a pre-blockade initiate
notification receiver (pre-blockade initiate notification receiver
162) configured to receive the pre-blockade initiate notification;
and a transmission-power increase processor (transmission-power
increase processor 166) configured to increase transmission power
upon receiving the pre-blockade initiate notification from the
pre-blockade initiate notification receiver.
[0009] In the radio communication system, a first radio base
station to be pre-blockaded reduces a transmission power while
second radio base stations near the first radio base station
increase transmission powers. Accordingly, when a communication
area of the first radio base station becomes smaller, communication
areas of the second radio base stations become larger. Thus, the
occurrence of an area in which no communication may be prevented,
so that the quality of the communication service is not
deteriorated.
[0010] A second feature of the present invention according to the
first feature is summarized as that the transmission-power
reduction processor reduces the transmission power in decrements of
a predetermined amount in a predetermined time period, and the
transmission-power increase processor increases the transmission
power in increments of the predetermined amount in the
predetermined time period.
[0011] A third feature of the present invention according to any
one of the first and second features is summarized as that the
first radio base station includes a distance measuring unit
(distance measuring unit 152) configured to measure a distance
between the first radio base station itself and the second radio
base station, and the pre-blockade initiate notification
transmitter transmits the pre-blockade initiate notification to the
second radio base station, the distance from which to the first
radio base station measured by the distance measuring unit is equal
to or smaller than a predetermined threshold.
[0012] A fourth feature of the present invention according to any
one of the first to third features is summarized as that the second
radio base station includes a direction specifying unit (direction
specifying unit 164) configured to specify a direction in which the
first radio base station exists, and the transmission-power
increase processor increases the transmission power in the
direction in which the first radio base station exists, the
direction being specified by the direction specifying unit.
[0013] A fifth feature of the present invention according to any
one of the first to fourth features is summarized as that the first
radio base station includes an ongoing-call absence notification
transmitter (ongoing-call absence notification transmitter 158)
configured to transmit the second radio base station an
ongoing-call absence notification indicating that there is no
on-going call anymore, when there is no ongoing call anymore in the
first radio base station, the second radio base station includes an
ongoing-call absence notification receiver (ongoing-call absence
notification receiver 168) configured to receive the ongoing-call
absence notification, and the transmission-power increase processor
stops increasing the transmission power when the ongoing-call
absence notification receiver receives the ongoing-call absence
notification.
[0014] A sixth feature of the present invention according to any
one of the first to fifth features is summarized as that the radio
communication system further including a base station controller
configured to connect the first radio base station and the second
radio base station to each other and to control the first radio
base station and the second radio base station, wherein the
pre-blockade initiate notification transmitter transmits the
pre-blockade initiate notification to the second radio base station
via the base station controller.
[0015] A seventh feature of the present invention is summarized as
a radio base station constituting a radio communication system, the
radio base station including: a storage unit configured to store
information on a different radio base station neighboring the radio
base station itself; a pre-blockade initiate notification
transmitter configured to transmit a pre-blockade initiate
notification indicating initiation of a pre-blockade to the
different radio base station identified based on the information on
the different radio base station stored in the storage unit, in
initiating the pre-blockade; and a transmission-power reduction
processor configured to reduce transmission power.
[0016] An eighth feature of the present invention is summarized as
a radio base station constituting a radio communication system, the
radio base station including: a pre-blockade initiate notification
receiver configured to receive a pre-blockade initiate notification
from a different radio base station, the pre-blockade initiate
notification indicating initiation of a pre-blockade in the
different radio base station; and a transmission-power increase
processor configured to increase transmission power when the
pre-blockade initiate notification receiver receives the
pre-blockade initiate notification.
[0017] A ninth feature of the present invention is summarized as a
blockade control method in a radio communication system including a
first radio base station and a second radio base station
neighboring the first radio base station, the method including the
steps of: the first radio base station transmitting a pre-blockade
initiate notification indicating initiation of a pre-blockade to
the second radio base station identified based on information on
the second radio base station stored in a storage unit, when the
first radio base station initiates the pre-blockade; the first
radio base station reducing transmission power; the second radio
base station receiving the pre-blockade initiate notification; and
the second radio base station increasing transmission power upon
receiving the pre-blockade initiate notification.
[0018] A tenth feature of the present invention is summarized as a
radio communication system (radio communication system 10)
including: a first radio base station (radio base station 1); and a
second radio base station (radio base stations 2A to 2F)
neighboring the first radio base station, wherein the first radio
base station includes: a storage unit (storage unit 103) configured
to store information on the second radio base station; a
transmitter (pre-blockade initiate notification transmission
processor 154) configured to transmit a preparation signal to the
second radio base station identified based on the information on
the second radio base station stored in the storage unit, before
blockade processing is performed; and a transmission-power
reduction processor (transmission-power reduction processor 156)
configured to reduce transmission power, and the second radio base
station includes a receiver (pre-blockade initiate notification
receiver 162) configured to receive the preparation signal; a
transmission-power increase processor (transmission-power increase
processor 166) configured to increase transmission power in
accordance with the preparation signal received by the
receiver.
[0019] An eleventh feature of the present invention is summarized
as that the transmission-power reduction processor reduces the
transmission power in accordance with a transmission-power
reduction rate, and the transmission-power increase processor
increases the transmission power in accordance with a
transmission-power increase rate.
[0020] A twelfth feature of the present invention is summarized as
that the first radio base station includes a distance measuring
unit (distance measuring unit 152) configured to measure a distance
between the first radio base station itself and the second radio
base station, and the transmitter transmits the preparation signal
to the second radio base station, the distance from which to the
first radio base station measured by the distance measuring unit is
equal to or smaller than a predetermined threshold.
[0021] A thirteenth feature of the present invention is summarized
as that the second radio base station includes a direction
specifying unit (direction specifying unit 164) configured to
specify a direction in which the first radio base station exists,
and the transmission-power increase processor increases the
transmission power in the direction in which the first radio base
station exists, the direction being specified by the direction
specifying unit.
[0022] A fourteenth feature of the present invention is summarized
as that the first radio base station includes an ongoing-call
absence notification transmitter (ongoing-call absence notification
transmitter 158) configured to transmit the second radio base
station an ongoing-call absence notification indicating that there
is no on-going call anymore, when there is no ongoing call anymore
in the first radio base station, the second radio base station
includes an ongoing-call absence notification receiver
(ongoing-call absence notification receiver 168) configured to
receive the ongoing-call absence notification, and the
transmission-power increase processor stops increasing the
transmission power when the ongoing-call absence notification
receiver receives the ongoing-call absence notification.
[0023] A fifteenth feature of the present invention is summarized
as the radio communication system further including a base station
controller configured to connect the first radio base station and
the second radio base station to each other and to control the
first radio base station and the second radio base station, wherein
the transmitter transmits the preparation signal to the second
radio base station via the base station controller.
[0024] A sixteenth feature of the present invention is summarized
as a radio base station which performs blockade processing
including: a storage unit configured to store information on a
different radio base station neighboring the radio base station
itself; a transmitter configured to transmit a preparation signal
to the second radio base station identified based on the
information on the different radio base station stored in the
storage unit, before blockade processing is performed; and a
transmission-power reduction processor configured to reduce
transmission power.
[0025] A seventeenth feature of the present invention is summarized
as a radio base station connected to a blockade radio base station
which performs blockade processing, the radio base station
including: a receiver configured to receive a preparation signal
transmitted from the blockade radio base station before the
blockade processing is performed; and a transmission-power increase
processor configured to increase transmission power in accordance
with the preparation signal received by the receiver.
[0026] An eighteenth feature of the present invention is summarized
as that the first radio base station includes: a blockade processor
(blockade processor 258) configured to measure a reception level of
the second radio base station when there is no ongoing call anymore
in the first radio base station itself; and a
transmission-power-change stop notification transmitter
(transmission-power-change stop notification transmitter 259)
configured to transmit a transmission-power-change stop
notification to the second radio base station, the reception level
of which measured by the blockade processor has reached or exceeded
a threshold, and the second radio base station includes a
transmission-power-change stop notification reception processor
(transmission-power-change stop notification reception processor
268) configured to stop the increase of the transmission power upon
receiving the transmission-power-change stop notification.
[0027] According to the present invention, deterioration of quality
of communication service may be prevented. Moreover, according to
the present invention, provided are a radio communication system, a
radio base station, and a blockade control method which can improve
the quality of the communication service by suppressing a
disconnection in a part of area during a blockaded processing in a
base station.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is an overall schematic configuration diagram of a
radio communication system of an embodiment of the present
invention.
[0029] FIG. 2 is a configuration diagram of a radio base station of
the embodiment of the present invention.
[0030] FIG. 3 is a first functional block configuration diagram of
a controller in the radio base station of the embodiment of the
present invention.
[0031] FIG. 4 is a view showing an example of position information
of a different radio base station.
[0032] FIG. 5 is a view showing an example of a pre-blockade
initiate notification.
[0033] FIG. 6 is a view showing an example of an ongoing-call
absence notification.
[0034] FIG. 7 is a second functional block configuration diagram of
a controller in the radio base station of the embodiment of the
present invention.
[0035] FIG. 8 is a sequence diagram showing an operation of the
radio communication system of the embodiment of the present
invention.
[0036] FIG. 9 is an overall schematic configuration diagram of the
radio communication system during pre-blockade processing of the
embodiment of the present invention.
[0037] FIG. 10 is a first functional block configuration diagram of
a controller in a radio base station of an additional
embodiment.
[0038] FIG. 11 is a second functional block configuration diagram
of a controller in a radio base station of the additional
embodiment.
[0039] FIG. 12 is a sequence diagram showing an operation of the
radio communication system of the additional embodiment.
[0040] FIG. 13 is a flowchart showing an operation of a first radio
base station of the additional embodiment.
MODES FOR CARRYING OUT THE INVENTION
First Embodiment
[0041] Next, a first embodiment of the present invention will be
described with reference to the drawings. Specifically,
descriptions will be given of (1) a configuration of a radio
communication system, (2) an operation of a radio base station, (3)
advantageous effects, and (4) other embodiments. In the following
description of the drawings, same or similar reference numerals
denote same or similar elements and portions.
(1) Configuration of Radio Communication System
[0042] First, the configuration of the radio communication system
of the embodiment of the present invention will be described in the
order of (1.1) an overall schematic configuration of the radio
communication system and (1.2) a configuration of the radio base
station.
(1.1) Overall Schematic Configuration of Radio communication
System
[0043] FIG. 1 is an overall schematic configuration diagram of a
radio communication system 10 of the embodiment of the present
invention.
[0044] The radio communication system 10 shown in FIG. 1 adopts LTE
(Long Term Evolution) which is a standard defined by 3GPP (Third
Generation Partnership Project). As shown in FIG. 1, the radio
communication system 10 includes a radio base station 1, radio base
stations 2A to 2F located around the radio base station 1, and a
base station controller 6. The radio communication system 10
provides a radio terminal 5 with a radio communication service.
[0045] The radio base station 1 transmits a radio signal at a
predetermined transmission power and provides a cell 3 being a
communication area. Similarly, the radio base stations 2A to 2F
transmit radio signals at predetermined powers and provide cells 4A
to 4F being communication areas, respectively. Each of these cells
4A to 4F is radially divided from the corresponding one of the
radio base stations 2A to 2F into multiple sectors (not
illustrated). In FIG. 1, the radio terminal 5 exists in the cell 3
provided by the radio base station 1. Thus, the radio terminal 5
can transmit and receive radio signals to and from the radio base
station.
[0046] The base station controller 6 controls the radio base
station 1 and the radio base stations 2A to 2F. The base station
controller 6 is connected to the radio base station 1 and the radio
base stations 2A to 2F by a wired line not illustrated.
(1.2) Configuration of Radio Base Station
[0047] FIG. 2 is a configuration diagram of the radio base station
1. As shown in FIG. 2, the radio base station 1 includes a
controller 102, a storage unit 103, a wired communication unit 104,
a radio communication unit 106, and an antenna 108. Note that, the
radio base stations 2A to 2F each have a configuration similar to
the radio base station 1.
[0048] The controller 102 is formed of a CPU for example, and
controls various functions included in the radio base station 1.
The storage unit 103 is formed of a memory for example, and stores
various types of information used for a control performed in the
radio base station 1 and the like.
[0049] The wired communication unit 104 transmits and receives data
to and from the base station controller 6. The radio communication
unit 106 includes a RF circuit, a baseband circuit, and the like,
and performs modulation, demodulation, coding, decoding, and the
like. The radio communication unit 106 transmits and receives radio
signals to and from the radio terminal 5 via the antenna 108.
[0050] FIG. 3 is a functional block configuration diagram of the
controller 102 in the radio base station 1. As shown in FIG. 3, the
controller 102 in the radio base station 1 includes a distance
measuring unit 152, a pre-blockade initiate notification
transmission processor 154, a transmission-power reduction
processor 156, and an ongoing-call absence notification
transmission processor 158.
[0051] The distance measuring unit 152 measures the distance
between the radio base station 1 and a different radio base
station.
[0052] Specifically, the storage unit 103 stores therein the
longitude and the latitude of the radio base station 1 being this
radio base station. Moreover, the storage unit 103 stores therein
position information of the different radio base station. FIG. 4 is
a view showing an example of position information of a different
radio base station. The position information of the different radio
base station shown in FIG. 4 includes an ID (base station ID) of
the corresponding radio base station and the longitude and the
latitude being the position of the corresponding radio base
station.
[0053] The distance measuring unit 152 measures the distance
between the radio base station 1 and the different radio base
station on the basis of the longitude and the latitude of the radio
base station 1 and the longitude and the latitude of the different
radio base station which are stored in the storage unit 103.
[0054] The pre-blockade initiate notification transmission
processor 154 identifies the base station ID of the different radio
base station whose distance from the radio base station 1 is equal
to or smaller than a predetermined threshold, on the basis of the
distance between the radio base station 1 and each of radio base
stations therearound which is measured by the distance measuring
unit 152. Here, the pre-blockade initiate notification transmission
processor 154 recognizes the radio base stations 2A to 2F as nearby
radio base stations whose distances from the radio base station 1
are equal to or smaller than the predetermined threshold, and
identifies the base station IDs thereof.
[0055] Next, when a request for a pre-blockade processing is made,
the pre-blockade initiate notification transmission processor 154
generates a pre-blockade initiate notification indicating that the
radio base station 1 is to start pre-blockade. Specifically, the
pre-blockade initiate notification transmission processor 154 sets
a transmission-power reduction rate indicating a reduction amount
of the transmission power per unit time and an initiation time of
the pre-blockade, and, in addition, generates the pre-blockade
initiate notification whose destinations are set to the radio base
stations 2A to 2F corresponding to the identified base station IDs.
Here, the initiation time of the pre-blockade is a time obtained by
adding a predetermined time period to a time when the pre-blockade
is requested by a network manager or the like.
[0056] FIG. 5 is a view showing an example of the pre-blockade
initiate notification. The pre-blockade initiate notification shown
in FIG. 5 includes the base station ID (here, ID of the radio base
station 1) of the radio base station being the transmission source
of the pre-blockade initiate notification, the base station ID
(here, IDs of the radio base stations 2A to 2F) of the radio base
station being the destination, the transmission-power reduction
rate in the pre-blockade, and the initiation time of the
pre-blockade.
[0057] Moreover, the pre-blockade initiate notification
transmission processor 154 outputs the generated pre-blockade
initiate notification to the wired communication unit 104. The
wired communication unit 104 transmits the pre-blockade initiate
notification to the radio base stations 2A to 2F via the base
station controller 6.
[0058] When the set initiation time of the pre-blockade comes, the
transmission-power reduction processor 156 reduces the transmission
power from the antenna 108 in accordance with the set
transmission-power reduction rate, and also inhibits reception of a
new call from the radio terminal 5.
[0059] The ongoing-call absence notification transmission processor
158 judges whether there is an ongoing call in the radio base
station 1. For example, if a communication between the radio
terminal 5 and the radio base station 1 is being performed, in
other words if there is an ongoing call, the radio terminal 5
cannot perform communication with the radio base station 1 after
the radio base station 1 reduces the transmission power in
accordance with the transmission-power reduction rate. Then, the
radio terminal 5 attempts a handover to the radio base station 2A
or the like.
[0060] When there is no ongoing call, the ongoing-call absence
notification transmission processor 158 generates an ongoing-call
absence notification. Specifically, the ongoing-call absence
notification transmission processor 158 sets a time (power down
time) when the transmission power in the radio base station 1
reaches zero, and generates the ongoing-call absence notification
whose destinations are set to the radio base stations 2A to 2F
corresponding to the base station IDs identified by the
pre-blockade initiate notification transmission processor 154. The
power down time is a time obtained by adding a predetermined time
period to a time when it is judged that there is no ongoing call in
the radio base station 1.
[0061] FIG. 6 is a view showing an example of the ongoing-call
absence notification. The ongoing-call absence notification shown
in FIG. 6 includes the base station ID (here, ID of the radio base
station 1) of the radio base station being the transmission source
of the ongoing-call absence notification, the base station ID
(here, IDs of the radio base stations 2A to 2F) of the radio base
station being the destination, and the power down time.
[0062] Furthermore, the ongoing-call absence notification
transmission processor 158 outputs the generated ongoing-call
absence notification to the wired communication unit 104. The wired
communication unit 104 transmits the ongoing-call absence
notification to the radio base stations 2A to 2F via the base
station controller 6.
[0063] Thereafter, the transmission-power reduction processor 156
performs a control to reduce the transmission power from the
antenna 108 to zero when the set power down time comes.
[0064] FIG. 7 is a functional block configuration diagram of the
controller 102 in the radio base stations 2A to 2F. As shown in
FIG. 7, the controller 102 in each of the radio base stations 2A to
2F includes a pre-blockade initiate notification reception
processor 162, a direction specifying unit 164, a
transmission-power increase processor 166, and an ongoing-call
absence notification reception processor 168.
[0065] The pre-blockade initiate notification reception processor
162 receives the pre-blockade initiate notification from the radio
base station 1 via the base station controller 6 and the wired
communication unit 104.
[0066] The direction specifying unit 164 specifies a direction in
which the radio base station 1 being the transmission source of the
pre-blockade initiate notification exists.
[0067] Specifically, the storage unit 103 stores therein the
longitude and the latitude of the one of the radio base stations 2A
to 2F which is this radio base station, as similar to the storage
unit 103 in the radio base station 1. Moreover, the storage unit
103 stores therein the position information of the different base
stations.
[0068] The direction specifying unit 164 extracts the transmission
source base station ID in the pre-blockade initiate notification,
and identifies a piece of the position information including the
extracted transmission source base station ID from the position
information of the different base stations stored in the storage
unit 103. Then, the direction specifying unit 164 specifies the
direction in which the radio base station 1 exists on the basis of
the longitude and the latitude in the identified piece of the
position information, in other words the longitude and the latitude
of the radio base station 1 being the transmission source of the
pre-blockade initiate notification, and on the basis of the
longitude and the latitude of the radio base station itself stored
in the storage unit 103.
[0069] The transmission-power increase processor 166 sets an
increase amount of the transmission power per unit time
(transmission-power increase rate) on the basis of the
transmission-power reduction rate in the pre-blockade initiate
notification. Specifically, the transmission-power increase
processor 166 causes the increase amount of the transmission power
per unit time to match the absolute value of the reduction amount
of the transmission power per unit time which is indicated by the
transmission-power reduction rate.
[0070] Furthermore, when the initiation time of the pre-blockade in
the pre-blockade initiate notification comes, the
transmission-power increase processor 166 increases the
transmission power from the antenna 108 in accordance with the set
transmission-power increase rate. At this time, the
transmission-power increase processor 166 increases only the
transmission power of a radio signal directed to a sector in a
direction specified by the direction specifying unit 164 among
radio signals directed to the sectors constituting the
corresponding one of the cells 4A to 4F.
[0071] The ongoing-call absence notification reception processor
168 receives the ongoing-call absence notification from the radio
base station 1 via the base station controller 6 and the wired
communication unit 104.
[0072] Thereafter, the transmission-power reduction processor 156
stops the increase of the transmission power from the antenna 108
when the power down time in the ongoing-call absence notification
comes, and controls the transmission power to be maintained at a
predetermined value. Here, the predetermined value is such a value
that the cells 4A to 4F of the radio base stations 2A to 2F include
the radio base station 1.
(2) Operation of Radio Communication System
[0073] Next, an operation of the radio communication system 10 will
be described. FIG. 8 is a flowchart showing an operation of the
radio communication system 10.
[0074] In step S100, the controller 102 in the radio base station 1
measures the distance between the radio base station 1 and each of
the different radio base stations.
[0075] In step S101, when the pre-blockade processing is requested,
the controller 102 in the radio base station 1 generates the
pre-blockade initiate notification which includes the
transmission-power reduction rate and the initiation time of the
pre-blockade and whose destinations are set to the radio base
stations 2A to 2F each located at such a position that distance
therefrom to the radio base station 1 is smaller than the
predetermined threshold.
[0076] In step S102, the controller 102 in the radio base station 1
transmits the pre-blockade initiate notification to the base
station controller 6. The base station controller 6 receives the
pre-blockade initiate notification from the radio base station 1.
Then, in step S103, the base station controller 6 transmits the
pre-blockade initiate notification to the radio base stations 2A to
2F. The controller 102 in each of the radio base stations 2A to 2F
receives the pre-blockade initiate notification from the base
station controller 6.
[0077] In step S104, the controller 102 in each of the radio base
stations 2A to 2F specifies the direction in which the radio base
station 1 exists.
[0078] Thereafter, in step S105, when the set pre-blockade
initiation time comes, the controller 102 in the radio base station
1 reduces the transmission power from the antenna 108 in accordance
with the set transmission-power reduction rate, and also inhibits
reception of a new call from the radio terminal 5.
[0079] Meanwhile, in step S106, the controller 102 in each of the
radio base stations 2A to 2F identifies a sector in the specified
direction in which the radio base station 1 exists as a sector
being a target of transmission power increase. Moreover, the
controller 102 in each of the radio base stations 2A to 2F sets the
transmission-power increase rate in accordance with the
transmission-power reduction rate included in the received
pre-blockade initiate notification. Furthermore, when the
pre-blockade initiation time included in the received pre-blockade
initiate notification comes, the controller 102 in each of the
radio base stations 2A to 2F reduces the transmission power from
the antenna 108 in accordance with the set transmission-power
reduction rate.
[0080] In step S107, the controller 102 in the radio base station 1
judges whether there is an ongoing call to the radio base station
1. If there is an ongoing call, the reduction of the transmission
power in the radio base station 1 in step S105 and the increase of
the transmission powers in the radio base stations 2A to 2F in step
S106 are continued.
[0081] If the communication between the radio terminal 5 and the
radio base station 1 is continued, in other words if there is an
ongoing call, the radio terminal 5 cannot perform communication
with the radio base station 1 after the radio base station 1
reduces the transmission power in accordance with the
transmission-power reduction rate, and attempts a handover to the
radio base station 2A or the like. Hence, if the reduction of the
transmission power in the radio base station 1 and the increase of
the transmission powers in the radio base stations 2A to 2F
therearound are continued, no ongoing call to the radio base
station 1 eventually exists.
[0082] On the other hand, if there is no ongoing call, the
controller 102 in the radio base station 1 generates the
ongoing-call absence notification which includes the power down
time and whose destinations are set to the radio base stations 2A
to 2F.
[0083] In step S108, the controller 102 in the radio base station 1
transmits the ongoing-call absence notification to the base station
controller 6. The base station controller 6 receives the
ongoing-call absence notification from the radio base station 1.
Then, in step S109, the base station controller 6 transmits the
ongoing-call absence notification to the radio base stations 2A to
2F. The controller 102 in each of the radio base stations 2A to 2F
receives the ongoing-call absence notification from the base
station controller 6.
[0084] Thereafter, in step S110, when the set power down time
comes, the controller 102 in the radio base station 1 performs such
a control that the transmission power from the antenna 108 becomes
zero.
[0085] Meanwhile, in step S111, when the power down time included
in the received ongoing-call absence notification comes, the
controller 102 in each of the radio base stations 2A to 2F performs
such a control that the increase of transmission power from the
antenna 108 is stopped and the transmission power is maintained at
the predetermined value.
(3) Advantageous Effects
[0086] In the radio communication system 10 of the embodiment of
the present invention, the radio base station 1 to be pre-blockaded
reduces the transmission power while the radio base stations 2A to
2F around the radio base station 1 increase the transmission
powers.
[0087] FIG. 9 is an overall schematic configuration diagram of the
radio communication system 10 during pre-blockade processing. By
comparing FIG. 9 and FIG. 1, it can be seen that the cell 3 being
the communication area of the radio base station 1 becomes smaller
while the cells 4A to 4F being the communication areas of the radio
base stations 2A to 2F become larger. This prevents a case where an
area in which the communication cannot be performed is formed and a
new call is not accepted.
[0088] Moreover, even if a new call from the radio terminal 5
existing in the cell 3 of the radio base station 1 before the
pre-blockade processing is received by one of the radio base
stations 2A to 2F, the quality of communication is maintained after
the pre-blockade processing, since the cells 4A to 4F being the
communication areas of the radio base station 2A to 2F are made
larger.
[0089] Moreover, the absolute value of the reduction rate of
transmission power in the radio base station 1 is equal to the
absolute value of the increase rate of transmission power in each
of the radio base stations 2A to 2F. In addition, the start timing
of the reduction of transmission power in the radio base station 1
is synchronized with the start timing of the increase of
transmission power in each of the radio base stations 2A to 2F.
Furthermore, the transmission power of the radio base station 1 is
gradually reduced, while the transmission power of each of the
radio base stations 2A to 2F is gradually increased in accordance
with the rate of reduction of the transmission power of the radio
base station 1.
[0090] Accordingly, the radio terminal 5 (see FIGS. 1 and 9)
existing inside the cell 3 of the radio base station 1 before the
pre-blockade processing and existing outside the cell 3 of the
radio base station 1 in the pre-blockade processing can
continuously perform communication by performing a handover to
switch from the radio base station 1 to any one of the radio base
stations 2A to 2F in the pre-blockade processing. Thus, forced
disconnection of the ongoing call is prevented, and the
pre-blockade processing can be performed anytime.
[0091] In addition, the radio base station 1 transmits the
pre-blockade initiate notification to only the radio base stations
2A to 2F being close to the radio base station 1 itself, in other
words the radio base stations 2A to 2F capable of including areas
being beyond the range of the cell 3 of the radio base station 1 in
the pre-blockade processing in the communication areas thereof by
increasing the transmission powers thereof, and prompt the radio
base stations 2A to 2F to increase the transmission powers thereof.
This suppresses unnecessary transmission of the pre-blockade
initiate notification and also increase of processing load due to
unnecessary increase of transmission power.
[0092] Moreover, each of the radio base stations 2A to 2F specifies
the direction in which the radio base station 1 exists, and
increases the transmission power of a radio signal directed to a
sector in that direction but does not increase the transmission
power of radio signals directed to other directions. This prevents
increase of interference caused in a case where the cells 4A to 4F
of the radio base stations 2A to 2F are each enlarged in a shape of
a perfect circle and regions overlapping with the cells of the
adjacent radio base stations become larger.
[0093] Furthermore, the radio base station 1 transmits the
ongoing-call absence notification to the radio base stations 2A to
2F if there is no ongoing call to the radio base station 1 itself.
At the same timing, the radio base station 1 reduces the
transmission power to zero, and the radio base stations 2A to 2F
each stops the control of increasing the transmission power and
maintains the transmission power at the predetermined value. This
prevents a case where the transmission powers of the radio base
stations 2A to 2F are continuously increased and the interference
is thus increased.
(4) Other Embodiments
[0094] As described above, the present invention has been described
by using the embodiments. However, it should not be understood that
the description and drawings which constitute part of this
disclosure limit the present invention. From this disclosure,
various alternative embodiments, examples, and operation techniques
will be easily found by those skilled in the art.
[0095] In the embodiment described above, the radio base station 1
transmits the pre-blockade initiate notification and the
ongoing-call absence notification to the radio base stations 2A to
2F via the base station controller 6. However, the notifications
may be transmitted directly to the radio base stations 2A to 2F
without being transmitted via the base station controller 6.
[0096] In the embodiment described above, descriptions are given of
the case where the radio base station 1 to be pre-blockaded reduces
the transmission power while the radio base stations 2A to 2F
located around the radio base station 1 increase the transmission
powers. However, the present invention can be similarly applied to
a case where one of the radio base stations 2A to 2F is to be
pre-blockaded and reduces the transmission power while the radio
base station 1 increases the transmission power.
[0097] In such case, the controller 102 in the one of the radio
base stations 2A to 2F has the functional block configuration shown
in FIG. 2, and the controller 102 in the radio base station 1 has
the functional block configuration shown in FIG. 6.
[0098] As described above, it should be understood that the present
invention includes various embodiments which are not described
herein. Accordingly, the technical scope of the present invention
should be determined only by the matters to define the invention in
the scope of claims regarded as appropriate based on the
disclosure.
Second Embodiment
[0099] Next, a second embodiment of the present invention will be
described with reference to the drawings. Specifically,
descriptions will be given of (1) a configuration of a radio
communication system, (2) an operation of a radio base station, (3)
advantageous effects, and (4) other embodiments. In the following
description of the drawings, same or similar reference numerals
denote same or similar elements and portions.
(1) Configuration of Radio Communication System
[0100] First, the configuration of the radio communication system
of the embodiment of the present invention will be described in the
order of (1.1) an overall schematic configuration of the radio
communication system and (1.2) a configuration of the radio base
station.
(1.1) Overall Schematic Configuration of Radio communication
System
[0101] FIG. 1 is an overall schematic configuration diagram of a
radio communication system 10 of the embodiment of the present
invention.
[0102] As shown in FIG. 1, the radio communication system 10
includes a radio base station 1, radio base stations 2A to 2F
located around the radio base station 1, and a base station
controller 6. The radio communication system 10 provides a radio
terminal 5 with a radio communication service.
[0103] The radio base station 1 transmits a radio signal at a
predetermined transmission power and provides a cell 3 being a
communication area. Similarly, the radio base stations 2A to 2F
transmit radio signals at predetermined powers and provide cells 4A
to 4F being communication areas, respectively. Each of these cells
4A to 4F is radially divided from the corresponding one of the
radio base stations 2A to 2F into multiple sectors (not
illustrated). In FIG. 1, the radio terminal 5 exists in the cell 3
provided by the radio base station 1. Thus, the radio terminal 5
can transmit and receive radio signals to and from the radio base
station.
[0104] The base station controller 6 controls the radio base
station 1 and the radio base stations 2A to 2F. The base station
controller 6 is connected to the radio base station 1 and the radio
base stations 2A to 2F by a wired line not illustrated.
(1.2) Configuration of Radio Base Station
[0105] FIG. 2 is a configuration diagram of the radio base station
1. As shown in FIG. 2, the radio base station 1 includes a
controller 102, a storage unit 103, a wired communication unit 104,
a radio communication unit 106, and an antenna 108. Note that, the
radio base stations 2A to 2F each have a configuration similar to
the radio base station 1.
[0106] The controller 102 is formed of a CPU for example, and
controls various functions included in the radio base station 1.
The storage unit 103 is formed of a memory for example, and stores
various types of information used for a control performed in the
radio base station 1 and the like.
[0107] The wired communication unit 104 transmits and receives data
to and from the base station controller 6. The radio communication
unit 106 includes a RF circuit, a baseband circuit, and the like,
and performs modulation, demodulation, coding, decoding, and the
like. The radio communication unit 106 transmits and receives radio
signals to and from the radio terminal 5 via the antenna 108.
[0108] FIG. 3 is a functional block configuration diagram of the
controller 102 in the radio base station 1. As shown in FIG. 3, the
controller 102 in the radio base station 1 includes a distance
measuring unit 152, a pre-blockade initiate notification
transmission processor 154, a transmission-power reduction
processor 156, and an ongoing-call absence notification
transmission processor 158.
[0109] The distance measuring unit 152 measures the distance
between the radio base station 1 and a different radio base
station.
[0110] Specifically, the storage unit 103 stores therein the
longitude and the latitude of the radio base station 1 being this
radio base station. Moreover, the storage unit 103 stores therein
position information of the different radio base station. FIG. 4 is
a view showing an example of position information of a different
radio base station. The position information of the different radio
base station shown in FIG. 4 includes an ID (base station ID) of
the corresponding radio base station and the longitude and the
latitude being the position of the corresponding radio base
station.
[0111] The distance measuring unit 152 measures the distance
between the radio base station 1 and the different radio base
station on the basis of the longitude and the latitude of the radio
base station 1 and the longitude and the latitude of the different
radio base station which are stored in the storage unit 103.
[0112] The pre-blockade initiate notification transmission
processor 154 identifies the base station ID of the different radio
base station whose distance from the radio base station 1 is equal
to or smaller than a predetermined threshold, on the basis of the
distance between the radio base station 1 and each of radio base
stations therearound which is measured by the distance measuring
unit 152. Here, the pre-blockade initiate notification transmission
processor 154 recognizes the radio base stations 2A to 2F as nearby
radio base stations whose distances from the radio base station 1
are equal to or smaller than the predetermined threshold, and
identifies the base station IDs thereof.
[0113] Next, when a request for a pre-blockade processing is made,
the pre-blockade initiate notification transmission processor 154
generates a pre-blockade initiate notification (preparation signal)
indicating that the radio base station 1 is to start pre-blockade.
Specifically, the pre-blockade initiate notification transmission
processor 154 sets a transmission-power reduction rate indicating a
reduction amount of the transmission power per unit time and an
initiation time of the pre-blockade, and, in addition, generates
the pre-blockade initiate notification whose destinations are set
to the radio base stations 2A to 2F corresponding to the identified
base station IDs. Here, the initiation time of the pre-blockade is
a time obtained by adding a predetermined time period (time period
with margin) to a time when the pre-blockade is requested by a
network manager or the like.
[0114] FIG. 5 is a view showing an example of the pre-blockade
initiate notification. The pre-blockade initiate notification shown
in FIG. 5 includes the base station ID (here, ID of the radio base
station 1) of the radio base station being the transmission source
of the pre-blockade initiate notification, the base station ID
(here, IDs of the radio base stations 2A to 2F) of the radio base
station being the destination, the transmission-power reduction
rate in the pre-blockade, and the initiation time of the
pre-blockade.
[0115] Moreover, the pre-blockade initiate notification
transmission processor 154 outputs the generated pre-blockade
initiate notification to the wired communication unit 104. The
wired communication unit 104 transmits the pre-blockade initiate
notification to the radio base stations 2A to 2F via the base
station controller 6.
[0116] When the set initiation time of the pre-blockade comes, the
transmission-power reduction processor 156 reduces the transmission
power from the antenna 108 in accordance with the set
transmission-power reduction rate, and also inhibits reception of a
new call from the radio terminal 5.
[0117] The ongoing-call absence notification transmission processor
158 judges whether there is an ongoing call in the radio base
station 1. For example, if a communication between the radio
terminal 5 and the radio base station 1 is being performed, in
other words if there is an ongoing call, the radio terminal 5
cannot perform communication with the radio base station 1 after
the radio base station 1 reduces the transmission power in
accordance with the transmission-power reduction rate. Then, the
radio terminal 5 attempts a handover to the radio base station 2A
or the like.
[0118] When there is no ongoing call, the ongoing-call absence
notification transmission processor 158 generates an ongoing-call
absence notification. Specifically, the ongoing-call absence
notification transmission processor 158 sets a time (power down
time) when the transmission power in the radio base station 1
reaches zero, and generates the ongoing-call absence notification
whose destinations are set to the radio base stations 2A to 2F
corresponding to the base station IDs identified by the
pre-blockade initiate notification transmission processor 154. The
power down time is a time obtained by adding a predetermined time
period (time period with margin) to a time when it is judged that
there is no ongoing call in the radio base station 1.
[0119] FIG. 6 is a view showing an example of the ongoing-call
absence notification. The ongoing-call absence notification shown
in FIG. 6 includes the base station ID (here, ID of the radio base
station 1) of the radio base station being the transmission source
of the ongoing-call absence notification, the base station ID
(here, IDs of the radio base stations 2A to 2F) of the radio base
station being the destination, and the power down time.
[0120] Furthermore, the ongoing-call absence notification
transmission processor 158 outputs the generated ongoing-call
absence notification to the wired communication unit 104. The wired
communication unit 104 transmits the ongoing-call absence
notification to the radio base stations 2A to 2F via the base
station controller 6.
[0121] Thereafter, the transmission-power reduction processor 156
performs a control to reduce the transmission power from the
antenna 108 to zero when the set power down time comes.
[0122] FIG. 7 is a functional block configuration diagram of the
controller 102 in the radio base stations 2A to 2F. As shown in
FIG. 7, the controller 102 in each of the radio base stations 2A to
2F includes a pre-blockade initiate notification reception
processor 162, a direction specifying unit 164, a
transmission-power increase processor 166, and an ongoing-call
absence notification reception processor 168.
[0123] The pre-blockade initiate notification reception processor
162 receives the pre-blockade initiate notification from the radio
base station 1 via the base station controller 6 and the wired
communication unit 104.
[0124] The direction specifying unit 164 specifies a direction in
which the radio base station 1 being the transmission source of the
pre-blockade initiate notification exists.
[0125] Specifically, the storage unit 103 stores therein the
longitude and the latitude of the one of the radio base stations 2A
to 2F which is this radio base station, as similar to the storage
unit 103 in the radio base station 1. Moreover, the storage unit
103 stores therein the position information of the different base
stations.
[0126] The direction specifying unit 164 extracts the transmission
source base station ID in the pre-blockade initiate notification,
and identifies a piece of the position information including the
extracted transmission source base station ID from the position
information of the different base stations stored in the storage
unit 103. Then, the direction specifying unit 164 specifies the
direction in which the radio base station 1 exists on the basis of
the longitude and the latitude in the identified piece of the
position information, in other words the longitude and the latitude
of the radio base station 1 being the transmission source of the
pre-blockade initiate notification, and on the basis of the
longitude and the latitude of the radio base station itself stored
in the storage unit 103.
[0127] The transmission-power increase processor 166 sets an
increase amount of the transmission power per unit time
(transmission-power increase rate) on the basis of the
transmission-power reduction rate in the pre-blockade initiate
notification. Specifically, the transmission-power increase
processor 166 causes the increase amount of the transmission power
per unit time to match the absolute value of the reduction amount
of the transmission power per unit time which is indicated by the
transmission-power reduction rate.
[0128] Furthermore, when the initiation time of the pre-blockade in
the pre-blockade initiate notification comes, the
transmission-power increase processor 166 increases the
transmission power from the antenna 108 in accordance with the set
transmission-power increase rate. At this time, the
transmission-power increase processor 166 increases only the
transmission power of a radio signal directed to a sector in a
direction specified by the direction specifying unit 164 among
radio signals directed to the sectors constituting the
corresponding one of the cells 4A to 4F.
[0129] The ongoing-call absence notification reception processor
168 receives the ongoing-call absence notification from the radio
base station 1 via the base station controller 6 and the wired
communication unit 104.
[0130] Thereafter, the transmission-power reduction processor 156
stops the increase of the transmission power from the antenna 108
when the power down time in the ongoing-call absence notification
comes, and controls the transmission power to be maintained at a
predetermined value. Here, the predetermined value is such a value
that the cells 4A to 4F of the radio base stations 2A to 2F include
the radio base station 1.
(2) Operation of Radio Communication System
[0131] Next, an operation of the radio communication system 10 will
be described. FIG. 8 is a flowchart showing an operation of the
radio communication system 10.
[0132] In step S100, the controller 102 in the radio base station 1
measures the distance between the radio base station 1 and each of
the different radio base stations.
[0133] In step S101, when the pre-blockade processing is requested,
the controller 102 in the radio base station 1 generates the
pre-blockade initiate notification which includes the
transmission-power reduction rate and the initiation time of the
pre-blockade and whose destinations are set to the radio base
stations 2A to 2F each located at such a position that distance
therefrom to the radio base station 1 is smaller than the
predetermined threshold.
[0134] In step S102, the controller 102 in the radio base station 1
transmits the pre-blockade initiate notification to the base
station controller 6. The base station controller 6 receives the
pre-blockade initiate notification from the radio base station 1.
Then, in step S103, the base station controller 6 transmits the
pre-blockade initiate notification to the radio base stations 2A to
2F. The controller 102 in each of the radio base stations 2A to 2F
receives the pre-blockade initiate notification from the base
station controller 6.
[0135] In step S104, the controller 102 in each of the radio base
stations 2A to 2F specifies the direction in which the radio base
station 1 exists.
[0136] Thereafter, in step S105, when the set pre-blockade
initiation time comes, the controller 102 in the radio base station
1 reduces the transmission power from the antenna 108 in accordance
with the set transmission-power reduction rate, and also inhibits
reception of a new call from the radio terminal 5. As for the
reduction of transmission power in accordance with the
transmission-power reduction rate, the transmission power may be
reduced in decrements of a constant amount for every constant time
period, or reduced in a continuous time period.
[0137] Meanwhile, in step S106, the controller 102 in each of the
radio base stations 2A to 2F identifies a sector in the specified
direction in which the radio base station 1 exists as a sector
being a target of transmission power increase. Moreover, the
controller 102 in each of the radio base stations 2A to 2F sets the
transmission-power increase rate in accordance with the
transmission-power reduction rate included in the received
pre-blockade initiate notification. Furthermore, when the
pre-blockade initiation time included in the received pre-blockade
initiate notification comes, the controller 102 in each of the
radio base stations 2A to 2F reduces the transmission power from
the antenna 108 in accordance with the set transmission-power
reduction rate.
[0138] In step S107, the controller 102 in the radio base station 1
judges whether there is an ongoing call to the radio base station
1. If there is an ongoing call, the reduction of the transmission
power in the radio base station 1 in step S105 and the increase of
the transmission powers in the radio base stations 2A to 2F in step
S106 are continued. Note that, the operation of step S107 is
performed periodically.
[0139] If the communication between the radio terminal 5 and the
radio base station 1 is continued, in other words if there is an
ongoing call, the radio terminal 5 cannot perform communication
with the radio base station 1 after the radio base station 1
reduces the transmission power in accordance with the
transmission-power reduction rate, and attempts a handover to the
radio base station 2A or the like. Hence, if the reduction of the
transmission power in the radio base station 1 and the increase of
the transmission powers in the radio base stations 2A to 2F
therearound are continued, no ongoing call to the radio base
station 1 eventually exists.
[0140] On the other hand, if there is no ongoing call, the
controller 102 in the radio base station 1 generates the
ongoing-call absence notification which includes the power down
time and whose destinations are set to the radio base stations 2A
to 2F.
[0141] In step S108, the controller 102 in the radio base station 1
transmits the ongoing-call absence notification to the base station
controller 6. The base station controller 6 receives the
ongoing-call absence notification from the radio base station 1.
Then, in step S109, the base station controller 6 transmits the
ongoing-call absence notification to the radio base stations 2A to
2F. The controller 102 in each of the radio base stations 2A to 2F
receives the ongoing-call absence notification from the base
station controller 6.
[0142] Thereafter, in step S110, when the set power down time
comes, the controller 102 in the radio base station 1 performs such
a control that the transmission power from the antenna 108 becomes
zero.
[0143] Meanwhile, in step S111, when the power down time included
in the received ongoing-call absence notification comes, the
controller 102 in each of the radio base stations 2A to 2F performs
such a control that the increase of transmission power from the
antenna 108 is stopped and the transmission power is maintained at
the predetermined value.
(3) Advantageous Effects
[0144] In the radio communication system 10 of the embodiment of
the present invention, the radio base station 1 to be pre-blockaded
reduces the transmission power while the radio base stations 2A to
2F around the radio base station 1 increase the transmission
powers.
[0145] FIG. 8 is an overall schematic configuration diagram of the
radio communication system 10 during pre-blockade processing. By
comparing FIG. 8 and FIG. 1, it can be seen that the cell 3 being
the communication area of the radio base station 1 becomes smaller
while the cells 4A to 4F being the communication areas of the radio
base stations 2A to 2F become larger. This prevents a case where an
area in which the communication cannot be performed is formed and a
new call is not accepted.
[0146] Moreover, since the cells 4A to 4F being the communication
areas of the radio base stations 2A to 2F are made larger, the call
from the radio terminal 5 existing in the cell 3 of the radio base
station 1 before the pre-blockade processing can be handed over to
one of the radio base stations 2A to 2F, and the quality of
communication of the ongoing call can be maintained.
[0147] Moreover, the absolute value of the reduction rate of
transmission power in the radio base station 1 is equal to the
absolute value of the increase rate of transmission power in each
of the radio base stations 2A to 2F. In addition, the start timing
of the reduction of transmission power in the radio base station 1
is synchronized with the start timing of the increase of
transmission power in each of the radio base stations 2A to 2F.
Furthermore, the transmission power of the radio base station 1 is
gradually reduced, while the transmission power of each of the
radio base stations 2A to 2F is gradually increased in accordance
with the rate of reduction of the transmission power of the radio
base station 1.
[0148] Accordingly, the radio terminal 5 (see FIGS. 1 and 8)
existing inside the cell 3 of the radio base station 1 before the
pre-blockade processing and existing outside the cell 3 of the
radio base station 1 in the pre-blockade processing can
continuously perform communication by performing a handover to
switch from the radio base station 1 to any one of the radio base
stations 2A to 2F in the pre-blockade processing. Thus, forced
disconnection of the ongoing call is prevented, and the
pre-blockade processing can be performed anytime.
[0149] Moreover, the radio base station 1 transmits the
pre-blockade initiate notification to the radio base stations 2A to
2F within a certain range from the radio base station 1 itself, and
causes those radio base stations to increase the transmission
powers. Thus, the cell 3 of the radio base station 1 itself is
covered with the cells of the different radio base stations.
Accordingly, different radio base stations outside the certain
range from the radio base station 1 itself are not affected (In
other words, if the pre-blockade initiate notification transmission
is transmitted to the different radio base stations outside the
certain range, unnecessary increase in the transmission power and
increase in processing load can be suppressed).
[0150] In addition, if each of the cells 4A to 4F of the radio base
stations 2A to 2F within the certain range from the radio base
station 1 is enlarged in a shape of a perfect circle, regions
overlapping with the cells of the adjacent radio base stations
become larger. Thus, each of the radio base stations 2A to 2F
specifies the direction in which the radio base station 1 exists,
and increases the transmission power of a radio signal directed to
a sector in that direction but does not increase the transmission
power of the radio signals directed to the other directions. Thus,
the radio base stations 2A to 2F prevent increase of interference
caused due to the regions where the cells of the adjacent radio
base stations overlap each other becoming larger.
[0151] Furthermore, the radio base station 1 transmits the
ongoing-call absence notification to the radio base stations 2A to
2F and also reduces the transmission power to zero. Each of the
radio base stations 2A to 2F having received the ongoing-call
absence notification stops the control of increasing the
transmission power, and maintains the transmission power at the
predetermined value. This prevents a case where the transmission
powers of the radio base stations 2A to 2F are continuously
increased and the interference is thus increased.
(4) Other Embodiments
[0152] As described above, the present invention has been described
by using the embodiments. However, it should not be understood that
the description and drawings which constitute part of this
disclosure limit the present invention. From this disclosure,
various alternative embodiments, examples, and operation techniques
will be easily found by those skilled in the art.
[0153] In the embodiment described above, the radio base station 1
transmits the pre-blockade initiate notification and the
ongoing-call absence notification to the radio base stations 2A to
2F via the base station controller 6. However, the notifications
may be transmitted directly to the radio base stations 2A to 2F
without being transmitted via the base station controller 6.
[0154] In the embodiment described above, descriptions are given of
the case where the radio base station 1 to be pre-blockaded reduces
the transmission power while the radio base stations 2A to 2F
located around the radio base station 1 increase the transmission
powers. However, the present invention can be similarly applied to
a case where one of the radio base stations 2A to 2F is to be
pre-blockaded and reduces the transmission power while the radio
base station 1 increases the transmission power. In such case, the
controller 102 in the one of the radio base stations 2A to 2F has
the functional block configuration shown in FIG. 2, and the
controller 102 in the radio base station 1 has the functional block
configuration shown in FIG. 6.
[0155] An additional embodiment is described below. Note that, the
additional embodiment is an embodiment in which it is checked
whether the communication area covered by a radio base station 1
can be covered by an adjacent radio base station in the
pre-blockade processing, before the radio base station 1 turns off
the transmission power. In the descriptions below of a controller
102 shown in FIG. 10, components which are the same as those
described in "(1) Configuration of Radio Communication System" are
denoted with the same reference numerals.
[0156] FIG. 10 is a block diagram of the controller 102 of the
radio base station 1. As shown in FIG. 10, the controller 102 in
the radio base station 1 includes a measuring unit 252, a
pre-blockade initiate notification transmission processor 154, a
transmission-power reduction processor 156, a blockade processor
258, and a transmission-power-change stop notification transmitter
259.
[0157] FIG. 11 is a block diagram of a controller 102 of a radio
base station 2. As shown in FIG. 11, the controller 102 of the
radio base station 2 includes a pre-blockade initiate notification
reception processor 162, a direction specifying unit 164, a
transmission-power increase processor 166, and a
transmission-power-change stop notification reception processor
268.
[0158] FIG. 12 is a flowchart showing an operation of the radio
communication system of the additional embodiment.
[0159] In step S200, the controller 102 (measuring unit 252) in the
radio base station 1 measures the distance between the radio base
station 1 and different radio base stations, and also measures a
reception level (for example, RSSI) of the different radio base
stations. When the pre-blockade processing is requested, the
controller 102 (pre-blockade initiate notification transmission
processor 154) in the radio base station 1 makes the following
determination in step S201. Among radio base stations 2A to 2F
whose distances to the radio base station 1 are equal to or smaller
than a predetermined threshold, a radio base station whose
reception level (for example, RSSI) of the different radio base
station is equal to or larger than a certain level is determined as
an adjacent base station.
[0160] In step S201, the controller 102 (pre-blockade initiate
notification transmission processor 154) in the radio base station
1 generates a pre-blockade initiate notification (preparation
signal) which includes a transmission-power reduction rate and a
pre-blockade initiation time and whose destination is set to the
adjacent base station.
[0161] In step S102, the controller 102 (pre-blockade initiate
notification transmission processor 154) in the radio base station
1 transmits the pre-blockade initiate notification to the base
station controller 6. The base station controller 6 receives the
pre-blockade initiate notification from the radio base station 1.
Then, in step S103, the base station controller 6 transmits the
pre-blockade initiate notification to the adjacent base station.
The controller 102 (pre-blockade initiate notification reception
processor 162) in the adjacent base station receives the
pre-blockade initiate notification from the base station controller
6.
[0162] In step S104, the controller 102 (direction specifying unit
164) in the adjacent base station specifies the direction in which
the radio base station 1 exists.
[0163] Thereafter, in step S105, when the set pre-blockade
initiation time comes, the controller 102 (transmission-power
reduction processor 156) in the radio base station 1 reduces the
transmission power from the antenna 108 in accordance with the set
transmission-power reduction rate, and also inhibits reception of a
new call from the radio terminal 5.
[0164] Meanwhile, in step S106, the controller 102 (direction
specifying unit 164) in the adjacent base station indentifies a
sector in the specified direction in which the radio base station 1
exists as a sector being a target of transmission power increase.
Moreover, the controller 102 (transmission-power increase processor
166) in the adjacent base station indentifies sets the
transmission-power increase rate in accordance with the
transmission-power reduction rate included in the received
pre-blockade initiate notification. Furthermore, when the
pre-blockade initiation time included in the received pre-blockade
initiate notification comes, the controller 102 in the adjacent
base station reduces the transmission power from the antenna 108 in
accordance with the set transmission-power reduction rate.
[0165] In step S107, the controller 102 (blockade processor 258) in
the radio base station 1 judges whether there is an ongoing call to
the radio base station 1. If there is an ongoing call, the
reduction of the transmission power in the radio base station 1 in
step S105 and the increase of the transmission powers in the radio
base stations 2A to 2F in step S106 are continued. Note that, the
operation of step S107 is performed periodically.
[0166] If the communication between the radio terminal 5 and the
radio base station 1 is continued, in other words if there is an
ongoing call, the radio terminal 5 cannot perform communication
with the radio base station 1 after the radio base station 1
reduces the transmission power in accordance with the
transmission-power reduction rate, and attempts a handover to the
radio base station 2A or the like. Hence, if the reduction of the
transmission power in the radio base station 1 and the increase of
the transmission powers in the adjacent base station are continued,
no ongoing call to the radio base station 1 eventually exists.
[0167] Meanwhile, if there is no ongoing call, the controller 102
(blockade processor 258) in the radio base station 1 performs a
control (off-air) of reducing the transmission power from the
antenna 108 to zero in step S110.
[0168] Next, in step S202, the controller 102 (blockade processor
258) in the radio base station 1 monitors a signal strength (RSSI)
from the adjacent base station, and judges whether the signal
strength has reached or exceeded a certain threshold. If the signal
strength has reached or exceeded the certain threshold, the
controller 102 (transmission-power-change stop notification
transmitter 259) in the radio base station 1 transmits a
transmission-power-change stop notification to the corresponding
adjacent base station in step S203. In step S204, the base station
controller 6 having received the transmission-power-change stop
notification relays and transmits the transmission-power-change
stop notification to the adjacent base station being a target.
[0169] Then, in step S111, the controller 102
(transmission-power-change stop notification reception processor
268) of the adjacent base station stops the increase of the
transmission power from the antenna 108 upon receiving the
transmission-power-change stop notification, and performs a control
to maintain the increased transmission power.
[0170] FIG. 13 is a flowchart showing an operation of the radio
base station 1 of the additional embodiment. The distance between
the radio base station 1 and each of the different radio base
stations and the reception level of each of the different radio
base stations are already known.
[0171] When the pre-blockade processing is requested, the
controller 102 (measuring unit 252) in the radio base station 1
makes the following determination in step S201. Among the radio
base stations 2A to 2F whose distance to the radio base station 1
is equal to or smaller than the predetermined threshold, a radio
base station whose reception level (for example RSSI) is equal to
or larger than a certain level is determined as an adjacent base
station.
[0172] In step S102, the controller 102 (pre-blockade initiate
notification transmission processor 154) in the radio base station
1 transmits the base station controller 6 the pre-blockade initiate
notification which includes the transmission-power reduction rate
and the pre-blockade initiation time and whose destination is set
to the adjacent base station. Thereafter, in step S105, when the
set pre-blockade initiation time comes, the controller 102
(transmission-power reduction processor 156) in the radio base
station 1 reduces the transmission power from the antenna 108 in
accordance with the set transmission-power reduction rate, and also
inhibits reception of a new call from the radio terminal 5.
[0173] In step S107, the controller 102 (blockade processor 258) in
the radio base station 1 judges whether there is an ongoing call to
the radio base station 1. If there is an ongoing call, the
reduction of transmission power in the radio base station 1 in step
S105 and the increase of transmission power in the adjacent base
station are continued. On the other hand, if there is no ongoing
call, the controller 102 (blockade processor 258) in the radio base
station 1 performs the control (off-air) of reducing the
transmission power from the antenna 108 to zero in step S110.
[0174] Next, in step S202, the controller 102 (blockade processor
258) in the radio base station 1 judges whether the reception level
from the adjacent base station has reached or exceeded the certain
threshold. If the reception level has reached or exceeded the
threshold, the controller 102 (transmission-power-change stop
notification transmitter 259 of the radio base station 1 transmits
the transmission-power-change stop notification to the
corresponding adjacent base station in step S203. If the reception
level is smaller than the threshold, step S202 is repeated.
[0175] As described above, in the additional embodiment, it is
checked whether the communication area covered by the radio base
station 1 can be covered by the adjacent radio base station, before
the radio base station 1 turns off the transmission power. Thus, a
stable communication service is provided to the radio terminal
without having the connection area temporarily in a disconnection
state due to the pre-blockade processing.
[0176] Note that the entire content of Japanese Patent Application
No. 2009-043192 (filed on Feb. 25, 2009) and the entire content of
Japanese Patent Application No. 2009-144055 (filed on Jun. 17,
2009) are incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0177] A radio communication system, a radio base station, and a
blockade control method of the present invention prevent
deterioration of quality of communication service and are useful as
a radio communication system and the like.
* * * * *